Technical Abstract:
Genetic diversity of a S. sclerotiorum population from a single field was assessed by mycelial compatibility groups (MCGs) and presence of double stranded RNA (dsRNA). Thirty-seven isolates were obtained from scleritia on 31 diseased lentil plants in a field in eastern Washington. The sampled plants were at least one meter apart from one another. Growth rate was measured on PDA. MCGs were determined by pairing the isolates in all possible combinations on modified Patterson’s medium. All isolates were self-compatible, but were not compatible with others except for four isolates that were from a single plant and were fully inter-compatible. A total of 34 MCGs were found among the 37 isolates. The results show a high degree of diversity in MCG of S. sclerotiorum from a single field from the Pacific Northwest. Three dsRNAs with sizes of 0.7, 2.3 and 20.0 kbs were detected singly or in combination in 13 of the 37 strains and confirmed by enzymatic digestions using RNase-free DNase and RNase A at different salt concentrations. The presence of dsRNA was not related to MCGs or growth rates. The ecological role of these dsRNAs remains to be determined.